LED is one sort of solid semiconductor device, which is able to directly convert electric energy to light energy. Compared with traditional incandescent and fluorescent light, white LED possesses the advantages of low power consumption, high luminous efficiency, long working life, energy conservation and environmental friendliness, etc. Therefore, not only is it widely used in the field of daily lighting, but it also steps into the field of display equipment. Currently, the techniques of acquiring white LED can be divided into two classes: (1) adopting the combination of three LED chips that emit red, green and blue light; (2) adopting a monochromatic (blue or ultraviolet) LED chip to excite an appropriate fluorescent material. At present, white LED mainly utilizes the combination of a blue LED chip and phosphor powder Ce3+:YAG which can be excited effectively by blue light and emit yellow light, and then the lens principle is used to mix complementary yellow and blue light so as to provide white light.
For a structure that uses phosphor powder packaging, there are the following disadvantages: 1) phosphor powder excitation efficiency and light conversion efficiency are low; 2) the problem of inhomogeneity of phosphor particle size and dispersion cannot be effectively solved; 3) phosphor powder lacks a red luminescent component, making it hard to manufacture white LED with a low color temperature and a high color rendering index; 4) the light failure of phosphor powder is tremendous, resulting in short working life of white LED; 5) the poor physicochemical properties of phosphor powder fail to meet the development of high-power LED.